I'm sure GM & Ford will also have full size truck options in the coming years, but I doubt you will see quad motors & the sort of performance Rivian will provide.
First quoted forum post, not sure if it'll work, but I got some good details from a Rivian rep regarding bed size. See below:Dimensions are pretty similar to a modern Ford Ranger supercrew.
When you say support pieces are you referring to something to support the rearmost part of the sheetgoods, that hang beyond the tailgate?At the Mill Valley/SF event, I was told by Adam Gase that plywood will fit in the back of the R1T with the tailgate down. There are small wheel well bumps, so if you want a load to ride flat, underneath support pieces would likely have to be added in the back of the bed. In this case, you don't get to take advantage of the full depth of the bed, but the wheel well bumps are not major.